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Author Topic: Ash bow build ( an experiment in wood torture ) finished tiller  (Read 20723 times)

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Offline sleek

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Ash bow build ( an experiment in wood torture ) finished tiller
« on: February 15, 2012, 08:39:57 am »
I am building an ash bow and am having early set issues. I have the bow 66 inches long, going for 25 inch draw and 35 lbs. After only floor tillering the upper limb only is taking set. I haven't pushed to bow past ( if even to ) brace height yet and don't feel like I am using undue pressure to get it there. ( I have made more bows than I care to count at the moment so I have a fairly good feel for the amount of pressure required. ) I am getting 3/4 inch set in this limb about mid limb. The limb is 1 1/4 inch wide there. I am wondering if anybody else has had problems like this? The bow has an even floor tiller and hasn't had a hinge there either. the ring count is 16 rings per inch if that helps?

I am worried about this bow ( despite its light draw weight, short draw, and long ntn ) taking excessive set. Is there something about white ash that I don't know? This wood was cut about 1.5 months ago, been in stave form for 2 weeks and bow dimensions for 1 week. I don't think moisture is causing this problem. I am trying to use heat to correct this problem and may even pike the upper limb and make it the stronger of the two to hopefully reduce its set. Any remaining set I will probably flip the tips just enough to cancel out. Any thoughts on my thinking process, or reasons/solutions to my problem?
« Last Edit: February 26, 2012, 06:33:05 am by sleek »
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Offline Pappy

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Re: Ash bow build
« Reply #1 on: February 15, 2012, 08:52:23 am »
If I was gussing I would say it is to wet or still green.  :) That's about all I know of that would cause set that early on. :)
   Pappy
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blackhawk

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Re: Ash bow build
« Reply #2 on: February 15, 2012, 08:52:46 am »
I think your wood is too wet still. Let her sit for a few more weeks,and heat treat ash
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Offline PEARL DRUMS

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Re: Ash bow build
« Reply #3 on: February 15, 2012, 09:49:57 am »
Its green. Give it at least 6 months stave form, 3 months bow form.
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Offline sleek

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Re: Ash bow build
« Reply #4 on: February 15, 2012, 02:00:48 pm »
Well, being wet seemingly the problem, I will give it a good warming over the stove for a a few hours. Not so much a heat treat, but fore sure get it hot for a few hours. Wish I had a scale to measure any loss in weight. That would help allot here...
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Offline PEARL DRUMS

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Re: Ash bow build
« Reply #5 on: February 15, 2012, 02:04:18 pm »
Toss it under your bed for one month.  A quick heating over a wood stove wont do much at all.
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Offline Bevan R.

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Re: Ash bow build
« Reply #6 on: February 15, 2012, 02:07:33 pm »
Leave it in your car when you go to work. Windows rolled up. that will dehydrate it.
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Offline Buckeye Guy

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Re: Ash bow build
« Reply #7 on: February 15, 2012, 02:14:21 pm »
Yes its most likely high moister
Let it set another two weeks in the warm & dry then
with most of the white woods you can heat it  up and drive it out  at that point ,something that Osage does not like !
get it all warm enough to remove the bend you don't want & put in any you do want 
Then the next day heat treat it , and it should stay put . just give it a day or two to settle in after heat treating !
Let us know how it goes!
Guy
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mikekeswick

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Re: Ash bow build
« Reply #8 on: February 15, 2012, 02:17:51 pm »
Ash is like hickory - it likes to be dry. It is also way stronger in tension than it is in compression. A perfect candidate for a fairly heavily trapped back. So at the moment your belly is even weaker than it will be when dry and unless the back is highly crowned or you have trapped it already it is giving a double wammy effect on the belly.
Ash respondes fairly well to heat treating but won't hold much if any reflex when unstrung.
Ash was the wood I cut my teeth on. When you know how to treat it it can make really nice bows.
What limb width taper have you got? Are you following the correct tiller for the width profile?
When you recurve tips you shorten working limb or to put it another way increase stress without having the option of wider thinner limbs to accept the extra bend so you will get more set in the inner/mid limb thus losing cast.
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Offline sleek

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Re: Ash bow build
« Reply #9 on: February 16, 2012, 05:13:22 am »
I got a food scale. The bow weighs 590 grams. The length is 66.5 inches long, handle is 1 3/4 inches wide with the mid limb at 1 1/4 inch wide  tapering slowly down to 3/4 inch tips. Does that sound like a reasonable mass with a stiff handle bow? About 8 inches of the center dont bend and the handle is 1 inch thick. Does the mass it has sound like it is wet or dry?
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Offline sleek

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Re: Ash bow build
« Reply #10 on: February 16, 2012, 06:11:21 am »
I just got it to a low 4 inch brace and found the problem ( or at least one ) I have almost all the bending out the fades. What a novice tillering mistake, and to think I was stumped on it. oh well, I still want to know what yall think about the mass of this bow and its moisture contnet if yall have an opinion. Thanks!
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Offline DarkSoul

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Re: Ash bow build
« Reply #11 on: February 16, 2012, 06:33:29 am »
"This wood was cut about 1.5 months ago, been in stave form for 2 weeks and bow dimensions for 1 week."
Yes, it is still wet or green. If the wood is in bow dimensions, it needs about four weeks indoors to thoroughly dry. It can be done in one only if you force dry it in a heatbox. Putting it over the stove for a few hours won't cut it.

It is difficult (if not impossible) to guess if the wood is dry basing it only on the mass. If we have the volume as well as the mass, we can calculate specific gravity (density). But ash is highly variable, so the SG is not a solid number. Furthermore, the difference between a "wet"  and "dry"  bow stave can be as little as 5%, or in your case 30 grams.
Put the stave indoors in a dry spot. Weigh it every three days or so, and keep track of its moisture loss. When it does not lose any weight in a week or so, you're good to go. For now, do NOT bend the bow at all! Resist the temptation...
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Offline sleek

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Re: Ash bow build
« Reply #12 on: February 16, 2012, 07:06:11 am »
Well thanks for the advice again.  It seems as though between my last post and yours, I took the bow out and tillered it to 30 lbs at 22 inches. I hate to make it sound like I didnt heed good advice, but I really thought the bow was just bending to much in the fades. Actually I know it was because thats the only place there is set taken place. I got the limbs bending much more in the mid and outer limb.

I will place this on a form and take advantage of all the set in the fades and make it a deflex in the handle and reflexed mid limb bow. Heat treat that in then let it sit for a week and see what happens. Hope it works out well. I now need a moisture meter. Thanks for the advice guys, and please dont think I just ignored it, again, I saw all the bend in the fades and figured my set problem was there.
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mikekeswick

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Re: Ash bow build
« Reply #13 on: February 16, 2012, 07:46:48 am »
Moisture meters are pretty much a waste of time.
You need a humidity meter with a thermometer.
Look in TTB for the relative humidity/temperature scale. These things combined will tell you for definate when it's good to go.
Or just use feel. ;)
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Offline sleek

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Re: Ash bow build
« Reply #14 on: February 16, 2012, 08:10:04 am »
Thanks Mike, I will see about that set up. In the mean while, The bow is now at 520 grams after tillered to 30lbs at 23". It lost allot of weight. It comes out to 18.34 ounces. Going by the TBB IV page 92 on the mass principle, Shooting a 66 inch stiff handle bow at 30 lbs draw weight and 25 inches of draw ( my final tiller target ) I should be at 13.5 ounces.

I am still 5 ounces to much, but I have yet to narrow my massive tips and rech that last 2 inches of draw length. Apparently I have aslo to let the wood finish curing. Oh well, I reckon one week wont hurt anything. LIke I said, I am going to tie it to a form and shape it to a deflexed handle with reflexed mid limb design. More to come later. Thanks again...
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